Existing knowledgebases focus on popular concepts such as persons, organizations, and locations. However, there are a great number of concepts in addition to the most popular concepts. These additional concepts make up a long tail when concepts are plotted. Typically tail concepts may be found in concept-entity pairs, which are extracted from text documents. Currently, concept-entity pairs cover a limited number of entities per concept due to insufficient mentions in text. Moreover, because a tail concept often overlaps many other concepts, it is challenging to apply existing techniques to tail concepts.